I have an AKAI Terecorder Deluxe (1/2 track mono) that has been restored.

Last night I used it and noticed a variance in the treble as a tape was played so knowing that tape tension in units without pressure pads is important I put some resistance on the supply reel and the treble sounded better.

What exactly would the problem be?

Sounds like the felt pads in the supply reel table are either going bad or are not under the proper tension.

If it is a tension issue how would I adjust?

If it is the felt going bad I have at least 2-3 AKAI tape transports which are similar I could pull some parts for the reel tables from.

Make sure the playback head doesn't have any oxide on the surface...or possibly the head is wearing. Try other tapes..Possible the tape is aging and losing its pliability, not conforming to the head as well as it used to.

Noticed it on two tapes that do not exhibit this issue on my AKAI GX-255.

To me when turning the reel table when no tape is installed and play is engaged the reel seemed to be a little easier to spin than most AKAIs using one motor are.

May open it up this afternoon and have a look.

It could be entirely possible that the brake is slipping as it is just a round piece of rubber on a stud which presses against the botom part of the reel table during playback so the one part is stationary providing the necessary tape tension via the felt discs slipping against each other.

I intend to use this to eventually copy all 1/2 track mono tapes I have to my computer as I figure it's better to use a 1/2 track mono machine for that versus a 1/4 track stereo machine.

Next on my list is a 1/2 track stereo machine to properly copy the three 1/2 track stereo tapes I have.

Better to wind the 5-inch tape onto standard 7 " reels. and play it that way.

Better even than that is to use like the record labels use - a 7-inch reel with a NAB hub - holds up to 1000 ft of a normal 1.5 mil 1200 foot roll of normal 7-inch tape - i.e. plenty of room for the 600 ft of the same tape on a 5 inch reel. In short - if it fits on a 5 inch it will fit on here and play a lot better.